The objectives of this project are to study human blood group and related membrane antigens on normal and malignant cells. Use is made of the automated hemagglutination-inhibition method for detecting and quantitating these antigens in human tissues and body fluids, on the membranes of cultured human cells and on malignant cells passaged in vivo in laboratory animals. Especial emphasis is placed on the quantitation and purification by affinity chromatography of blood group I antigen, and the use of antisera against this antigen,purified from malignant cells, will be investigated for diagnostic potential.